In the container industry, empty containers are arranged into a pattern before the containers are moved for further processing. Often the patterned containers are moved onto a pallet for shipping. Round or circular containers are typically arranged into a nested pattern of rows and columns in which the containers of one row partially fit into the space between the containers of an adjacent row.
Circular and square containers can be self-patterning. Rows or streams of containers are placed on a conveyor and move to a pattern forming area. The incoming containers impact against the containers already in the pattern forming area, and the impact forces urge the containers to arrange themselves into the pattern.
When the receiving area receives enough containers to fill a pallet, the patterned containers are held in the pattern by a sweep. The sweep moves the patterned containers off the conveyor and onto the pallet. Examples of container palletizing systems that utilize self-patterning containers are disclosed in Simkowski, U.S. Pat. No. 5,522,692 and Slat et al. U.S. Pat. No. 5,733,100.
Not all containers are self-patterning. FIG. 1 illustrates portions of two rows R1 and R2 of non-round containers A forming part of a nested pattern of containers. Each container A includes convex front and rear surfaces B and convex side surfaces C. In forming the pattern, a container A in row R2 impacts against a pair of containers A in row R1. The impact force represented by the arrow I generates a torque T on the impacted containers in row R1. The torque T urges the containers to rotate. Containers A on the ends of row R1 may rotate 90 degrees and destroy the desired nested pattern.
Containers that are not self-patterning are often manually patterned. This is labor-intensive and the production rate is low.
Alternatively, rows of containers may be mechanically lifted from the conveyor and arranged in the desired pattern. Hischek et al. U.S. Pat. No. 6,688,839 discloses a container handling device that could possibly be adapted for use with non-self-patterning containers to move rows of containers from a conveyor belt and form a bottle pattern.
Such container handling devices are expensive, and the conveyors used with such handling devices must be dedicated for use with the handling device. Dedicated conveyors would remain idle during production runs of self-nesting containers.
Thus there is a need for an improved method for forming patterns of containers that are not self-patterning. The method should allow the use of conventional conveyors, and should enable the conveyors to be used with self-patterning containers.